[Fontconfig] Streamlining fontconfig scanning

[Lawrence D'Oliveiro]

On Thu, 10 Aug 2017 16:42:53 -0400, Keith Packard wrote:

> Lawrence D'Oliveiro <ldo at geek-central.gen.nz> writes:
> 
>> Should the extra validation be controlled by some kind of config
>> option?  
> 
> One could imagine a separate tool which would scan a font and display
> inconsistencies. We could encourage font packagers to use that tool
> when building packages so that distributions would at least be able
> to tell if there were broken fonts and perhaps provide a way to
> report bugs upstream.

And for those that remain unfixed, how about segregating them in a
separate directory, using an extra attribute on the <dir> directive:

    <dir assume_well_formed="yes|no">

where the “assume_well_formed” directive defaults to “no” if omitted.
That way the known-good fonts can be put in their own directories with
assume_well_formed="yes", and we get the speedup from bypassing the
extra checks on them, at least.